KR20190086716A - Method for producing flame-retardant foam and flame-retardant foam - Google Patents

Abstract

A method for producing a flame-retardant foam and a flame-retardant foam having high heat-insulating properties and excellent flame retardancy is provided. The flame-retardant foam is a molded article of a mixture containing at least a cellulose-containing powder, a hydrophilic polymer, a foamable thermoplastic resin, a flame retardant, and water. The mixture comprises at least one of tricalcium phosphate or silica as a dispersing agent.

Description

Method for producing flame-retardant foam and flame-retardant foam

The present invention relates to a flame retardant foam and a method for producing the flame retardant foam.

BACKGROUND ART Conventionally, many types of resin-based foams are known as heat insulating materials and cushioning materials. For example, as a heat insulating material for a building such as a house, a resin-based foam insulating material such as a mineral insulating material such as a glass fiber and a rock surface, a heat insulating material containing a natural component such as a cellulose fiber and a carbonated foam cork, a hard urethane foam and a polystyrene foam is known have. The components and methods of preparation of these foams have been studied and developed for improvement from a variety of perspectives such as use and desired properties.

For example, in conventional foams, there has been a problem that soot is generated at the time of burning for disposal of the foam, combustion calories per unit weight are high, and the environmental load is large. A solution to this problem has been proposed. For example, one proposed solution is to feed a paper powder and a hydrophilic polymer having a specific average particle diameter to a extruder in a specified amount, heat mix and then mix the water and the specific thermoplastic resin in the hot melt And a foam is obtained (Patent Document 1).

In the foam disclosed in Patent Document 1, not only the generation of the above-mentioned soot and the environmental load are suppressed, but also the foaming polypropylene as the thermoplastic resin and the specific kinds of polypropylene and polyethylene are added in predetermined amounts, Insulation is excellent.

Various investigations and developments have been conducted on foams as a heat insulator as described above. However, sufficient research and development have not been made to provide not only insulation but also flame retardancy to foams as insulation materials for houses and the like. In general, when the density is lowered by improving the foamability in order to obtain excellent heat resistance, since a large amount of air is contained, the flame retardancy tends to decrease. Therefore, it is not easy to realize both excellent heat insulation and excellent flame retardancy. In this regard, there is still a possibility of improvement for the solution proposed in Patent Document 1. [

Japanese Patent Application Laid-Open No. 2011-213966

SUMMARY OF THE INVENTION

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method for producing a flame-retardant foam and a flame-retardant foam which have high heat-insulating properties and excellent flame retardancy.

In order to solve the above problems, the flame retardant foam of the present invention comprises at least A cellulose-containing powder, a hydrophilic polymer, a foamable thermoplastic resin, a flame retardant, and water. The mixture comprises at least one of tricalcium phosphate or silica as a dispersing agent.

The method for producing a flame-retardant foam of the present invention includes a mixing step of preparing a mixture by mixing at least a cellulose-containing powder, a hydrophilic polymer, a flame retardant, a tricalcium phosphate or silica as a dispersant, and water. In addition, the method for producing a flame-retardant foam according to the present invention is characterized in that a particle-forming step in which the mixture obtained in the mixing step is assembled and a granular material obtained in the granulating step are heated and mixed with an expandable thermoplastic resin by an extruder , Extrusion and foaming steps for foaming molding.

According to the present invention, it is possible to provide a method for producing a flame-retardant foam and a flame-retardant foam having high heat-insulating property and excellent flame retardancy.

DETAILED DESCRIPTION OF THE INVENTION

Hereinafter, the production method of the flame-retardant foam and the flame-retardant foam of the present embodiment will be described in detail.

(Flame retardant foam)

The flame- A cellulose-containing powder, a hydrophilic polymer, a foamable thermoplastic resin, a flame retardant, and water. The mixture comprises tricalcium phosphate or silica as a dispersing agent.

The cellulose-containing powder may be selected from the group consisting of wood powder containing cellulose obtained by pulverizing hardwoods and conifers, and paper powder obtained by pulverizing waste paper, or a mixture of the wood powder and the paper powder in a predetermined amount ≪ / RTI >

Raw materials for paper powder include paper rolls of industrial waste; A variety of waste paper such as newspapers, magazines, printing paper, wrapping paper, cardboard and office paper; A phage and a defect paper obtained in the process of manufacturing a virgin paper; Waste remaining when cutting a magazine; Powder due to abrasion and wear; And grinder wastes and the like.

The average particle diameter of the cellulose-containing powder is preferably in a range of 30 占 퐉 to 200 占 퐉. The amount of the cellulose-containing powder relative to the total amount of the mixture is preferably in the range of 10 mass% to 20 mass%, more preferably in the range of 13 mass% to 15 mass%. By setting the average particle diameter and the amount of the cellulose-containing powder within the above-mentioned range, a flame-retardant foam having an appropriate thermal conductivity can be obtained.

Generally, if the amount of the cellulose-containing powder is too large, the bubble size becomes small and the density tends to become large. As a result, the thermal conductivity tends to become large (which means that the heat insulating property tends to deteriorate). On the other hand, if the amount of the cellulose-containing powder is too small, the bubble size tends to increase and the density tends to decrease. However, the convection of the gas in the bubble tends to increase also in this case (the heat insulating property tends to deteriorate it means).

The average particle diameter of the material used in the flame-retardant foam of the present embodiment can be measured using, for example, a commercially available laser diffraction type particle size distribution measuring apparatus (Mastersizer S manufactured by Marvern Instruments Ltd.).

The hydrophilic polymer may be at least one of a hydrophilic natural polymer and a hydrophilic synthetic polymer.

Hydrophilic natural polymers may include, for example, starch, Nikawa (glue), natural rubber and agar. Of these materials, starch can be particularly preferably used. The specific kind of starch is not particularly limited, and industrial starch and starch contained in corn, sweet potato, potato, wheat, barley and rice can be used.

Examples of the hydrophilic synthetic polymer include polyvinyl alcohol, acrylate, maleate, and the like. The hydrophilic polymer may be composed of one compound or a combination of two or more compounds.

The amount of the hydrophilic polymer relative to the total amount of the mixture is preferably 20 mass% or more and 30 mass% or less, and more preferably 24 mass% or more and 28 mass% or less. The amount of the hydrophilic polymer relative to the amount of the cellulose-containing powder is preferably 1.5 times or more and 2.5 times or less by mass. When the amount of the hydrophilic polymer is in the above range, a flame-retardant foam having an appropriate cell size can be obtained.

It is preferable that the expandable polyolefin-containing resin be used as the expandable thermoplastic resin. Specifically, foamable polypropylene can be used.

Generally, ordinary polypropylene has low foaming property because the tensile force in the molten state is weak, and therefore, it is not used as an optimal material for the foam. In this connection, foaming thermoplastic resins, which are polypropylene having a higher tensile strength than that of melting, have been developed in recent years. For example, "Newfoamer (registered trademark)" manufactured by Japan Polypropylene Corporation is commercially available as a foamable thermoplastic resin. Such a foamable thermoplastic resin can be suitably used for the flame retardant foam of the present embodiment.

The flame-retardant foam of the present embodiment may contain a conventional thermoplastic resin together with a foamable thermoplastic resin. As the conventional thermoplastic resin, a polyolefin-containing resin may be used. Specifically, a typical thermoplastic resin may include any one of polypropylene and polyethylene, or a combination of polypropylene and polyethylene in a predetermined amount. When an ordinary thermoplastic resin is contained, the amount of the ordinary thermoplastic resin is generally preferably not more than 1/2 by mass with respect to the amount of the expandable thermoplastic resin.

Examples of polypropylenes include block-polymerized polypropylene, random-polymerized polypropylene, homo-polymerized polypropylene, metallocene-polypropylene, and the like. Examples of the polyethylene include low density polyethylene, linear low density polyethylene, medium density polyethylene, high density polyethylene and metallocene-polyethylene.

In addition, in the flame retardant foam of the present embodiment, it may include a resin foaming facilitator together with a foamable thermoplastic resin and a conventional thermoplastic resin. As the resin foaming auxiliary, it is preferable to use anhydrous fumaric acid-modified polyolefin. Generally, the amount of the resin foaming auxiliary is preferably 1/20 or less by mass with respect to the amount of the expandable thermoplastic resin.

The anhydrous fumaric acid-modified polyolefin may exist between the cellulose-containing powder and the thermoplastic resin and between the hydrophilic polymer and the thermoplastic resin to improve the adhesion. Specifically, the olefin chain in the anhydrous fumaric acid-modified polyolefin is miscible with, for example, polypropylene, and the branch of anhydrous fumaric acid in the anhydrous fumaric acid-modified polyolefin reacts well with the OH group of the starch and the paper powder , An anhydrous fumaric acid-modified polyolefin is considered to function as a surfactant.

The total amount of the expandable thermoplastic resin, the conventional thermoplastic resin and the resin foam promoting agent is preferably in the range of 25 mass% or more and 40 mass% or less, and more preferably in the range of 31 mass% or more and 33 mass% or less, based on the total amount of the mixture . When the total amount of the foamable thermoplastic resin, the conventional thermoplastic resin and the resin foam promoting agent is within the above range, a flame retardant foam having an appropriate size of bubbles can be obtained. If the total amount of the foamable thermoplastic resin, the ordinary thermoplastic resin and the resin foam improver is too large, the size of the bubble becomes large, the thermal conductivity becomes high and the heat insulating property deteriorates. If the total amount is too small. The size of the bubble becomes small and the foaming becomes defective.

The flame retardant is a halogen-based flame retardant such as a bromine-containing flame retardant and a chlorine-containing flame retardant; Phosphorus flame retardants such as phosphoric acid esters, red phosphorus and inorganic phosphates; And inorganic hydride flame retardants such as aluminum hydroxide and magnesium hydroxide.

The flame retardant foam of the present embodiment is preferably an inorganic phosphate which is a phosphorus flame retardant from the viewpoint that there is little modification of the resin, less generation of gas during combustion, and low toxicity.

Further, the flame retardant preferably contains at least ammonium polyphosphate and ammonium phosphate. The ratio of the amount of ammonium polyphosphate to the amount of ammonium phosphate is preferably in the range of 3: 7 to 7: 3. The amount of ammonium polyphosphate is preferably approximately the same as the amount of ammonium phosphate. Use of a combination of a flame retardant that is a polymer and a flame retardant that is a monomer is preferable because flame retardancy such as a polymer flame retardant such as ammonium polyphosphate alone can be maintained and a blending amount of a required flame retardant can be reduced .

It is believed that the use of a combination of these two types of flame retardants is desirable due to the formation of foams from both the material burning in the gas phase and the material burning in the solid phase. In other words, the foam is formed from both a substance such as a thermoplastic resin from which a combustible gas is emitted and from a substance which burns in a gaseous phase at an appropriate concentration of oxygen in the air, and a substance which burns at a solid phase from a solid surface, such as a cellulose-containing powder and a hydrophilic polymer . Therefore, when two kinds of flame retardants are used in combination, it is considered that they act effectively on different types of combustion.

The blending amount of the flame retardant with respect to the total amount of the mixture is preferably in the range of 5% by mass or more and 20% by mass or less. When the blending amount of the flame retardant is within the above range, a flame-retardant foam having good foamability and excellent flame retardancy can be obtained. When the blending amount of the flame retardant is too large, the flame retardant foam becomes defective. On the other hand, when the blending amount of the flame retardant is too small, the flame retardant foam has unsatisfactory flame retardancy.

The flame-retardant foam of the present embodiment may preferably contain a polyhydric alcohol, a melamine or a melamine compound as a flame retarding aid.

As the polyhydric alcohol, pentaerythritol is preferably used. When polyhydric alcohols such as pentaerythritol are added as a flame retarding additive, the polyhydric alcohol imparts oxygen atoms to the polypropylene and leaves only the carbon layer by the dehydration reaction. Since the carbon layer prevents combustion, flame retardancy of the flame-retardant foam can be easily exhibited. In addition, melamine compounds such as melamine and melamine cyanurate and melamine polyphosphate can form a foamed layer by heating. Since such a foam layer prevents combustion, flame retardancy of the flame-retardant foam can be easily shown.

Tricalcium phosphate and silica as dispersing agents are added to improve the dispersibility of the cellulose-containing powder, the hydrophilic polymer, the flame retardant and the expandable thermoplastic resin and to obtain a more uniform mixture. As the dispersing agent, an inorganic dispersing agent is preferably used. When an organic dispersant is used, the flame retardancy may be lowered. The dispersant is preferably substantially insoluble in water. Each of tricalcium phosphate and silica may be used singly or in combination of both.

Examples of the silica used as the dispersing agent may include spherical silica, fused silica and crystalline silica. The above exemplified silicas can be used alone or in combination.

The blending amount of tricalcium phosphate or silica relative to the total amount of the mixture is in the range of 2% by mass or more and 8% by mass or less, preferably 5% by mass or more and 7.5% by mass or less. When the blending amount of the dispersing agent is too small, the dispersibility is not sufficiently exhibited. On the other hand, when the blending amount of the dispersing agent is too large, it becomes difficult to form particles from the mixture. The average particle diameter of the dispersing agent is preferably in the range of 4 μm or more and 7 μm or less. If the average particle diameter of the dispersing agent is out of this range, foaming may not occur properly.

The bulk density of the dispersant is preferably in the range of the loose bulk density (coarse filling density (density) of the loose powder when measured using a powder characteristic evaluation device (for example, Powder Tester (registered trademark) PT-X manufactured by Hosokawa Micron Corporation) : loosely filled density) of not more than 0.6 g / cm ³ . The bulk density of the dispersant is preferably 1.0 g / cm ³ or less with respect to the packed bulk density (density of packed wheat) when measured using the above-mentioned powder property evaluation apparatus.

When the blending amount, average particle diameter and bulk density of the dispersing agent are within the above ranges, it is possible to prevent dispersion of dispersion of the flame retardant particularly in the cellulose-containing powder and the hydrophilic polymer, thereby improving the foaming rate and flame retardancy.

Generally, as the expansion ratio increases and the density of the foam decreases, the flame retardancy tends to become lower as the air in the foam increases. However, when the dispersant is added, the expansion ratio (and the density is decreased) and the flame retardancy can be improved. As a result, a flame-retardant foam having excellent flame retardancy and high heat-insulating properties can be obtained.

The flame retardant foam of the present embodiment may include a powdery resin blowing agent or a liquid resin blowing agent to adjust the foaming state. Specifically, the acrylic-modified fluororesin can be used as a disperse resin foaming aid, and the silicone surfactant can be used as a liquid resin foaming aid.

When the acryl-modified fluororesin is used, the tensile force of the thermoplastic resin in the molten state can be improved and the foaming can be promoted. When a silicone surfactant is used, the surfactant can improve the expansion ratio by connecting a hydrophilic substance and a hydrophobic substance.

The flame-retarded foam of the present embodiment may contain additives other than the above-mentioned components, so long as the effect of the present invention is not impaired. Examples of additives include antioxidants, antibacterial agents and coloring agents.

(Production method of flame-retardant foam)

Next, one embodiment of a method for producing a flame-retardant foam will be described.

The method for producing a flame-retardant foam of the present embodiment includes a mixing step of mixing at least a cellulose-containing powder, a hydrophilic polymer, a flame retardant, a tricalcium phosphate or silica as a dispersing agent, and water to prepare a mixture. In addition, the production method of the flame-retardant foam of the present embodiment includes an assembling step of assembling the mixture obtained in the mixing step. In addition, the production method of the flame-retardant foam of the present embodiment includes an extrusion foaming step of heating and mixing the granular material obtained in the above-mentioned granulation step and a foamable thermoplastic resin by an extruder and performing foam molding.

In the mixing step, a mixture is prepared by mixing at least a predetermined amount of a cellulose-containing powder, a hydrophilic polymer, a flame retardant containing a flame retardant auxiliary, tricalcium phosphate or silica and water as a dispersing agent. Further, in the mixing step, a resin foam blowing agent or other components in a powder form and a liquid form can be added. In the mixing process, a mixer such as a ribbon-type mixer or a Henschel mixer can be used.

In the mixing process, it is preferred that the flame retardant is at least a homogeneous material such as ammonium polyphosphate and ammonium phosphate, and an inorganic phosphate which combines one of the water-resistant materials with one of the water-soluble materials. It is also preferable that the water-soluble ammonium phosphate is dissolved in water or hot water before mixing with other materials. When the ammonium phosphate is dissolved in water or hot water before mixing, the uniformity of the ammonium phosphate can be further increased and dispersed, and the absorption by the cellulose-containing powder and the hydrophilic polymer can be facilitated. As a result, the flame retardancy of the flame-retardant foam can be improved.

The amount of water to be added in the mixing step is in the range of 8% by mass or more and 15% by mass or less, preferably 10% by mass or more and 11.5% by mass or less based on the total amount of the mixture. When the amount of water is in the above range, subsequent assembly is promoted and a flame retardant foam having an appropriate foaming state can be obtained.

In the assembling step, the mixture obtained in the mixing step is formed into granules having a specific shape and size. The shape of the granular material may be various, such as pellets, spheres and discs. The size of the granular material may also vary. Preferably, for example, the mixture can be extruded in the form of a string from a pelletizing extruder and subsequently cut into pellets.

Next, in the extrusion foaming step, an extruder for producing a foam such as a biaxial extruder is firstly extruded with a granular material such as pellets produced by the granulation process, a foamable thermoplastic resin and, if necessary, a conventional thermoplastic resin and an anhydrous fumaric acid -Modified polyolefin is added.

In the interior of the extruder, the granular material such as pellets and the thermoplastic resin are heated, and the components are homogeneously kneaded by the screw of the extruder to obtain a hot melt.

In the interior of the extruder, a cellulose-containing powder, a hydrophilic polymer, a flame retardant, a dispersant, water and a foamable thermoplastic resin constituting a granular material such as pellets are heated and kneaded. In this process, the entire component is uniformly kneaded by the effect of the dispersant, thereby obtaining a high-temperature melt.

In the production method of the flame-retardant foam of the present embodiment, water may be further added in the extrusion foaming step. By introducing water into the cylinder of the extruder in the extrusion foaming step, the amount of water contained in the hot melt can be adjusted. The temperature of the water contained in the hot melt of this stage is higher than 100 캜; In order to keep the pressure high in the cylinder of the extruder, water does not vaporize. Then, when the hot melt is extruded from the die mounted at the tip of the extruder, the hot melt is opened to atmospheric pressure, so that water is vaporized in the melt to form bubbles therein. As a result, the melt expands. The expansion ratio of the melt to the original volume is preferably about 20 times or more and 40 times or less per unit volume. The amount of water added is adjusted so that the expansion ratio falls within the above range. Further, in order to adjust the temperature of the melt, hot water heated to a desired temperature may be added.

The hot melt is extruded from a die mounted at the tip of the extruder and cooled. In this case, when a die having a plurality of small holes is used in this process, a hot melt which is extruded from a small hole and appropriately expanded forms a plurality of stick-like foams, They are fusion-bonded to each other and formed into a plate. In addition, in the method of manufacturing the flame-retardant foam of the present embodiment, the flame-retardant foam may be molded in a desired form such as a sheet form by changing the shape of the die. The density of the flame-retardant foam is preferably in the range of 20 kg / m ³ to 50 kg / m ³ , more preferably in the range of 25 kg / m ³ to 35 kg / m ³ from the viewpoint of cost and strength .

By using the production method of the flame-retardant foam of the present embodiment described above, a flame-retardant foam having high heat-insulating property and excellent flame retardancy can be produced.

Hereinafter, the method for producing the flame-retardant foam and the flame-retardant foam of the present invention will be described in more detail by way of examples, but the present invention is not limited by the following examples.

Example

(Examples 1 to 3)

The following compounds were used as the thermoplastic resin (foamable thermoplastic resin, ordinary thermoplastic resin and resin blowing auxiliary), hydrophilic polymer, cellulose-containing powder, flame retardant (including flame retardant auxiliary), dispersant, and resin foaming auxiliary. The properties of the dispersant are shown in Table 1. The bulk density shown in Table 1 was measured using a powder property evaluation apparatus (Powder Tester (registered trademark) PT-X manufactured by Hosokawa Micron Corporation).

Foaming thermoplastic resin: Foaming polypropylene (FTS4000 manufactured by Japan Polypropylene Corporation)

Conventional thermoplastic resin: polypropylene (BC8 manufactured by Japan Polypropylene Corporation)

Resin foaming agent: Fumaric anhydride-modified polyolefin (Fusabond P613 manufactured by DuPont)

Hydrophilic polymer: starch (H-100 manufactured by Kato Kagaku Co., Ltd.)

Cellulose-containing powder: Paper powder (average particle diameter: 40 to 70 μm)

A mixture of flame retardant (including flame retarding auxiliary): ammonium polyphosphate, pentaerythritol, and melamine (Taien E manufactured by Taihei Chemical Industrial Co., Ltd.), ammonium phosphate (Taien N manufactured by Taihei Chemical Industrial Co., Ltd.)

Dispersant: tricalcium phosphate (tricalcium phosphate manufactured by Taihei Chemical Industrial Co., Ltd.)

Resin foaming aid (powder): Acryl-modified fluororesin (METABLEN A-3000 manufactured by Mitsubishi Rayon Co., Ltd.)

Resin foaming aid (liquid phase): A silicone surfactant (SH193 manufactured by Dow Corning Toray Co., Ltd.)

First, using a hydrophilic polymer, a cellulose-containing powder, a flame retardant (including a flame retardant auxiliary), a dispersant, a resin foaming aid (powder), a resin foaming aid (liquid) and water, And pellets were prepared by the assembling process. The amounts in Table 2 are in mass%.

Next, the pellets produced by the assembling step and the thermoplastic resin (expandable thermoplastic resin, ordinary thermoplastic resin, resin foam promoting agent) were put into an extruder in the amounts shown in Table 2 and mixed by heating. A flame-retardant foam was obtained.

(Example 4)

Except that silica (1) (ACEMATT (registered trademark) HK 400 manufactured by Evonik (Evonik industries AG)) shown in Table 1 was used as a dispersing agent, the components were measured in the same manner as in Examples 1 to 3 The flame retardant foam of Example 4 was obtained.

(Example 5)

Except that the silica (2) (ACEMATT (registered trademark) OK 520 manufactured by Evonik (Evonik industries AG)) shown in Table 1 was used as the dispersing agent, the components were measured in the same manner as in Examples 1 to 3 The flame retardant foam of Example 5 was obtained.

(Comparative Example 1)

Flame retardant foam of Comparative Example 1 was obtained in the same manner as in Examples 1 to 3 on the basis of the amounts in Table 2, with the exception that the dispersing agent was not used.

(Comparative Example 2)

The components were the same as in Examples 1 to 3 on the basis of the amounts in Table 2, except that calcium carbonate (1) shown in Table 1 (Softon 3200, manufactured by Bihoku Funka Kogyo Co., Ltd.) Flame retardant foam of Comparative Example 2 was obtained.

(Comparative Example 3)

The components were measured in the same manner as in Examples 1 to 3 on the basis of the amounts in Table 2, except that calcium carbonate (2) (BF200, manufactured by Bihoku Funka Kogyo Co., Ltd.) To obtain a flame retardant foam of Comparative Example 3.

(Comparative Example 4)

The components were measured in the same manner as in Examples 1 to 3 on the basis of the amounts in Table 2, except that calcium carbonate (3) (BF400, manufactured by Bihoku Funka Kogyo Co., Ltd.) To obtain a flame retardant foam of Comparative Example 4.

(Comparative Example 5)

(1) (GANZPEARL GB-05S manufactured by Aica Kogyo Co., Ltd.) shown in Table 1 was used as a dispersant, the components were measured in the same manner as in Examples 1 to 3 and A flame-retardant foam of Comparative Example 5 was obtained by the same method.

(Comparative Example 6)

The components were evaluated in the same manner as in Examples 1 to 3 and Comparative Examples 1 to 3 on the basis of the amounts in Table 2, except that the organic dispersant (2) (GRANDPEARL GU-0700P manufactured by Aica Kogyo Co., Ltd.) A flame retardant foam of Comparative Example 6 was obtained by the same method.

The flame retardancy, density, and heat insulating properties of the flame retardant foams of Examples 1 to 5 and Comparative Examples 1, 5, and 6 were measured and evaluated based on the following criteria. Comparative Example 2 containing calcium carbonate (1) having a small average particle diameter as a dispersant, Comparative Example 3 containing calcium carbonate (2) having a large bulk density, and Comparative Example 3 containing calcium carbonate having a large average particle diameter and high bulk density ), Defective foaming occurred in the extrusion foaming step. Further, in Comparative Examples 2, 3, and 4, it was impossible to obtain flame-retardant property, density, and heat insulating property because a foam in a plate-shape or sheet-shape could not be obtained. In Table 3, "production of foam" was evaluated as "poor" because no foam in the form of a plate or a sheet was obtained in Comparative Examples 2, 3 and 4, In the examples, "production of foam" in Table 3 was evaluated as "fair ".

<Flammability>

A specimen of 13 mm x 50 mm x 150 mm in size was cut from each of the flame retarded foams of Examples 1 to 5 and Comparative Examples 1, 5 and 6. The test piece was measured for burning time and burning distance of the test piece according to measurement method B in Annex B of JIS A 9521 "Building Insulation" and evaluated according to the following criteria.

(Combustion time)

A: Less than 120 seconds

B: 120 seconds to less than 125 seconds

C: 125 seconds or more

Is considered to be satisfactory, "B" is considered to be substantially satisfactory, and "C" is considered to be slightly unsatisfactory since short burning times are considered highly flammable.

(Combustion distance)

Titration: Less than 60 mm

Poor: 60 mm or more

Since the short firing distance is considered to be highly flammable, "titration" is considered to be substantially satisfactory and "poor" is considered to be somewhat unsatisfactory.

<Density>

A specimen of 13 mm x 50 mm x 150 mm in size was cut from each of the flame retarded foams of Examples 1 to 5 and Comparative Examples 1, 5 and 6. The density of each test specimen was measured and evaluated according to the following criteria.

A: 25 to 35 kg / m &lt; ³ &gt;

B: 36 to 50 kg / m &lt; ³ &gt;

C: 51 kg / m ³ or more

A "is considered to be satisfactory," B "is considered to be substantially satisfactory, and" C "is considered slightly unsatisfactory.

<Thermal Insulation>

A specimen of 13 mm x 50 mm x 150 mm in size was cut from each of the flame retarded foams of Examples 1 to 5 and Comparative Examples 1, 5 and 6. The thermal conductivity of each specimen was measured and evaluated according to the following criteria. The following evaluation criteria are set so that the flame retardant foam of the present invention having the thickness of 80 mm satisfies the energy conservation countermeasure grade 4 (thermal resistance value 2.2 m ² W / K) of the "Act on Promotion of Quality Assurance of Housing, etc.".

Titration: Less than 0.036 W / mK

Poor: 0.036 W / mK or more

Since the smaller the thermal conductivity is the better, "titration" is considered to be substantially satisfactory and "poor" is considered to be slightly unsatisfactory.

Table 3 shows the results of measurement and evaluation of the flame retardancy, density, and heat insulating properties.

As shown in Table 3, Examples 1 to 5 containing tricalcium phosphate or silica as a dispersant were all suitably evaluated in the comprehensive judgment based on flame retardancy, density and heat insulation. In the overall judgment, the examples in which all the evaluation items were only "appropriate", "A" or "B" were considered to be "problematic" as being almost no problem. Also, in the overall judgment, the examples having at least one "bad", "C", or "-" (impossible to evaluate) were regarded as "bad" as having a problem that can not be overlooked.

On the other hand, Comparative Example 1, which did not contain a dispersant, was evaluated to be inferior to Examples 1 to 5 in terms of combustion time, density, and heat insulation. Comparative Examples 5 and 6 including the organic dispersant were evaluated to be inferior in flame retardancy to Examples 1 to 5. Further, in Comparative Example 6, since the samples were all burnt in the combustibility test, the measurement of the combustion time and the combustion distance was not performed, and the extremely low density was obtained.

From the above results, it was confirmed that a flame-retardant foam having high heat-insulating property and excellent flame retardancy can be obtained by the production method of the flame-retardant foam of the present embodiment.

The flame-retardant foam of the present embodiment has the following characteristics.

The flame-retardant foam of the first embodiment is a molded article of a mixture containing at least a cellulose-containing powder, a hydrophilic polymer, a foamable thermoplastic resin, a flame retardant, and water. The mixture contains at least one of tricalcium phosphate or silica as a dispersing agent.

In this case, the dispersant improves the dispersibility of the cellulose-containing powder, the hydrophilic polymer, the flame retardant, and the expandable thermoplastic resin, and allows a more uniform mixture to be obtained. Due to this, the flame-retardant foam has high heat-insulating properties and excellent flame retardancy.

When the flame retardant foam of the second embodiment is realized in combination with the first embodiment, the flame retardant preferably includes inorganic phosphate.

In this case, the resin of the flame-retardant foam is hardly modified, gas generation at the time of combustion is reduced, and toxicity is lowered.

When the flame retardant foam of the third embodiment is realized in combination with the first or second embodiment, the flame retardant preferably includes at least ammonium polyphosphate and ammonium phosphate.

In this case, it is believed that ammonium polyphosphate and ammonium phosphate work effectively against different types of combustion, improving the flame retardancy of the flame retardant foam.

When the flame retardant foam of the fourth embodiment is realized in combination with any one of the first to third embodiments, the blending amount of the flame retardant is in the range of 5% by mass or more and 20% by mass or less with respect to the total amount of the mixture . The blending amount of the dispersing agent is preferably in the range of 2% by mass or more and 8% by mass or less based on the total amount of the mixture.

In this case, the flame-retardant foam has excellent foamability and excellent flame retardancy. Further, the mixture can be easily assembled.

When the flame retardant foam of the fifth embodiment is realized in combination with any one of the first to fourth embodiments, the mixture preferably includes pentaerythritol.

In this case, pentaerythritol imparts an oxygen atom to a foamable thermoplastic resin such as polypropylene and leaves only a carbon layer by dehydration reaction. Since the carbon layer prevents combustion, flame retardancy of the flame-retardant foam can be easily exhibited.

When the flame retardant foam of the sixth embodiment is realized in combination with any one of the first to fifth embodiments, the mixture preferably contains a melamine or a melamine compound.

In this case, the melamine or melamine compound forms a foamed layer by heating. Since such a foam layer prevents combustion, flame retardancy of the flame-retardant foam can be easily exhibited.

When the flame retardant foam of the seventh embodiment is realized in combination with any one of the first to sixth embodiments, the mixture preferably includes an anhydrous fumaric acid-modified polyolefin.

In this case, the anhydrous fumaric acid-modified polyolefin exists between the cellulose-containing powder and the thermoplastic resin and also between the hydrophilic polymer and the thermoplastic resin. This improves the adhesion between the cellulose-containing powder and the thermoplastic resin and between the hydrophilic polymer and the thermoplastic resin, thereby improving the foamability of the mixture.

The method for producing the flame-retardant foam of the eighth embodiment includes a mixing step of mixing at least one of cellulose-containing powder, hydrophilic polymer, flame retardant, dispersant, at least one of tricalcium phosphate or silica and water to prepare a mixture. The method also includes an assembling step of assembling the mixture obtained in the mixing step. In addition, the production method of the flame-retardant foam further includes an extrusion foaming step of heating and mixing the granular material obtained in the above-mentioned granulation step and the foamable thermoplastic resin by an extruder and performing foam molding.

In this case, the dispersant improves the dispersibility of the cellulose-containing powder, the hydrophilic polymer, the flame retardant and the expandable thermoplastic resin, and a more uniform mixture can be obtained. As a result, a flame-retardant foam having high heat insulation property and excellent flame retardancy can be obtained.

When the flame retardant foam of the ninth embodiment is realized in combination with the eighth embodiment, it is preferable that in the mixing process, the flame retardant is an inorganic phosphate containing at least ammonium polyphosphate and ammonium phosphate. It is preferable that the ammonium phosphate is dissolved in water or hot water before mixing.

In this case, it is believed that ammonium polyphosphate and ammonium phosphate act effectively on different types of combustion, thereby improving the flame retardancy of the flame retardant foam. Further, the uniformity of the ammonium phosphate can be increased and dispersed, the cellulose-containing powder and the hydrophilic polymer can be easily absorbed, and the flame retardancy of the flame-retardant foam can be improved.

When the method for producing a flame-retardant foam of the tenth embodiment is realized in combination with the eighth or ninth embodiment, it is preferable to further add water in the extrusion foaming step.

In this case, when water vaporizes, bubbles are formed inside the melt, and the melt is expanded. As a result, the expansion ratio of the flame-retardant foam can be improved.

Claims (10)

A flame-retardant foam which is a molding of a mixture comprising at least a cellulose-containing powder, a hydrophilic polymer, a foamable thermoplastic resin, a flame retardant and water,
Wherein the mixture comprises at least one of tricalcium phosphate or silica as a dispersing agent. The flame retardant foam of claim 1, wherein the flame retardant comprises an inorganic phosphate. The flame retardant foam of claim 1 or 2, wherein said flame retardant comprises at least ammonium polyphosphate and ammonium phosphate. The flame retardant composition according to any one of claims 1 to 3, wherein the blending amount of the flame retardant is in the range of 5 mass% to 20 mass% with respect to the total amount of the mixture, and the blending amount of the dispersing agent is 2 mass% 8% by mass or less. The flame retardant foam of any one of claims 1 to 4, wherein the mixture comprises pentaerythritol. The flame retardant foam according to any one of claims 1 to 5, wherein the mixture comprises a melamine or melamine compound. 7. A flame retardant foam according to any one of claims 1 to 6, wherein the mixture comprises anhydrous fumaric acid-modified polyolefin. A mixing step of mixing at least a cellulose-containing powder, a hydrophilic polymer, a flame retardant, at least one of tricalcium phosphate or silica as a dispersing agent, and water to prepare a mixture;
A particle-forming step of assembling the mixture obtained in the mixing step;
An extrusion and foaming step of heating and mixing the particles obtained in the granulation step with a foamable thermoplastic resin by an extruder and performing foam molding;
&Lt; / RTI &gt; 9. The method of claim 8, wherein in said mixing step said flame retardant is at least an inorganic phosphate comprising ammonium polyphosphate and ammonium phosphate,
Wherein the ammonium phosphate is dissolved in water or hot water before mixing. The method for manufacturing a flame-retardant foam according to claim 8 or 9, wherein water is further added in the extrusion blowing step.